It's Mitt Romney's campaign trail twist on the inspirational slogan from "Friday Night Lights," the gritty but poignant TV series about football at fictional Dillon High School in rural Texas. The popular version – simply "Clear eyes, full hearts, can't lose!" – has become a rallying cry for a resurgent Romney campaign.

Romney has repeated a version of the line for several days straight on the campaign trail. His campaign sent fundraising email with the motto in the subject line. And it's now plastered at the top of his Facebook page, overlaid on a black-and-white photo of the candidate standing in the rain, his back to the camera, at a rally in Virginia on Monday.

"Clear eyes, full heart, can't lose," Romney said Tuesday in Iowa as he recalled a young teenager facing certain death from cancer. "This is something that we share in this country, men and women of clear eyes and full hearts and America can't lose."

Left out of that speech was the refrain that has been his campaign slogan: "Believe in America."

The unofficial new motto came to prominence almost by accident.

"Friday Night Lights" is one of Romney's favorite TV shows. He and his wife, Ann, watched the series, which ran on NBC and DirecTV for five seasons, and they've even gotten some of their staff members hooked.

In the show, the phrase is Coach Eric Taylor's exhortation to his team, the Dillon Panthers. "Clear eyes, full hearts, can't lose," he'll say, sometimes quietly, in the locker room before a game or at halftime. "Can't lose!" the players yell back before running out onto the field, reaching up one at a time to tap a painted "P" logo on the locker room wall as they leave.

At several points during the presidential campaign, aides said, Romney has brought up the show and mentioned that particular line as inspirational.

On Oct. 3, the day of the first presidential debate, Romney's advisers knew: It was game day. After weeks of sliding in polls and facing questions about the direction of his campaign, would Romney come to play?

Some of his campaign aides went looking for ways to pump him up ahead of time.

Before going onstage, it turned out, Romney would wait in a locker room just off of the hockey rink at the University of Denver, as the arena had been converted into a debate hall. His campaign aides tacked family photos along the concrete walls in the hallway. Romney's grandchildren brought a game of Jenga to play while they waited.

And his "advance" team – the people charged with building Romney's events and making sure they run smoothly – erected a sign they'd had printed on the sly. "Clear eyes, full hearts, can't lose," it said, sitting in a metal frame perched over the door to the stage, the Romney "R" logo printed in the background.

As he walked underneath it and out toward the hall, Romney reached up and tapped the sign with his hand, mimicking the football players touching their team's logo. Romney's personal aide, Garrett Jackson, snapped a photo.

Then Romney took the stage opposite President Barack Obama, and had the game of his life. When he walked back underneath the sign, his entire staff was waiting in the hallway.